Each Navigraph AIRAC cycle costs 20 navigraph credits. The minimum amount of credits that you can buy for your navigraph account is 100 which costs about $12 AUD which means each cycle (approx 1 month) costs about $2.40 AUD. Each cycle contains a complete and updated collection of airways, weigh points and SIDS/STARS. Worth every dollar in my opinion.

The data changes all of the time. Someone has to do the work to put it into a format that the aircraft understands each time it gets updated by the governments (all around the world). The person who does this work for you would like to get paid for it (in the US, you could easily do it yourself with a little technical knowhow, and if someone says "Excel!" I'll hunt you down and slap you with a database book). Furthermore, for some countries, the data is not publicly available and requires the developer to pay for it.

Most add-on companies buy the first round of data to start you off when you buy their aircraft. After that, it's all on you.

If you look at companies now, you'll see that a lot of them don't make money based off of products. A lot of them make money on data and knowledge that others don't have. Ever wonder why SpeedTest.net is free to test your connection? They sell the stats of your test to ISPs.